Infections appear to be more frequent and severe in the elderly compared to the young population, and the aging of immune mechanisms may play a role. The effect of aging on cell-mediated immunity has been evaluated in several good studies, but our knowledge of the efficacy of PMN function and the acute inflammatory response is limited. We propose a one year pilot study of a broad range of PMN functions in healthy elderly volunteers, for the purpose of gathering baseline data which will be used in a subsequent RO-1 application. Specifically, we propose to measure the following: 1. Circulating PMN counts and marrow PMN mobilization. 2. Adherence to nylon fiber and to endothelial cell monolayers. 3. Random migration, chemotaxis, and chemotactic factor generation. 4. Chemiluminescence (phagocytosis and subsequent oxidative burst). 5. Degranulation/secretion. 6. Bacterial activity. 7. Skin-window test to measure the intensity of PMN delivery to sites of inflammation in vivo. Abnormalities discovered in the pilot study will become the focus of an RO-1 application examining mechanisms and implications. If no abnormalities are found, the pilot data will serve as baseline for a more extensive sequential study to determine whether or not the stress of illness will bring out defective PMN function not manifest in the steady state.